1. Field of the Invention
The present invention relates to a system for disabling or modifying an engine function to accommodate sensed weather conditions.
2. Background Art
Engines, such as compression ignition engines, use an engine controller that controls nearly every aspect of engine operation. Complex algorithms are incorporated in the engine control system that modify engine operation based upon inputs from sensors, data tables, and the like. Engine control systems optimize engine performance to maximize fuel economy and reduce engine emissions. Control algorithms may be used to control engine power output. Engine control systems may be specified by fleet managers to control operation of a fleet of vehicles to assure that drivers operate the vehicles in a safe and efficient manner.
Weather conditions may impact vehicle operation. Specifically, precipitation, such as rain, sleet or snow, may change desired driving patterns. For example, a safe driving speed for a dry road may be excessive if it is raining. Further, temperature may affect driving when roads are wet or covered with ice and snow. Wet or ice covered roads may make it desirable to limit vehicle speed and availability of engine braking systems.
Prior art engine controllers are not generally provided with information regarding precipitation. Further, while prior engine controls have had ambient temperature inputs, these temperature inputs were not used to control selected engine functions, such as engine braking or speed control, based upon weather conditions.
Fleet managers and prudent vehicle operators realize that fuel economy may be improved by limiting the maximum vehicle speed. However, in some instances, vehicle operators require the ability to exceed vehicle speed limitations temporarily for passing or when traveling over hilly terrain.
Engine braking systems have been developed to supplement or complement conventional vehicle brakes. One type of engine brake is a compression brake that functions by causing the exhaust valve to open prematurely near the end of the compression stroke. This causes air pressure from the cylinder to be released before its energy is returned to the crankshaft during the power stroke. As a result, the engine functions similar to an air compressor and can slow the vehicle down. Another type of engine brake is an exhaust brake. Exhaust brakes are located in the exhaust system downstream of the turbocharger. Exhaust brakes restrict the flow of exhaust gases out of the engine. Pressure builds up in the exhaust system so that when the piston expels gases from the cylinder during the exhaust stroke, exhaust gases must push against that pressure. This restriction in the exhaust system absorbs horsepower and can slow the vehicle down.
There is a need for a system that overrides engine calibrations based upon a determination that a vehicle is operating in an environment where precipitation is present and, in particular, where precipitation is present and ambient temperatures are below a predetermined level where ice and snow may be present on a road surface.
The present invention is directed to solving the above problems and fulfilling the needs described above.